A common radar system has an oscillator for generating a signal of frequency Fo, a distributor for splitting the signal of frequency Fo produced from the oscillator into two parts, and a frequency multiplier for multiplying the frequency of the signal of frequency Fo, which is a signal split by the distributor, and for outputting a signal of frequency 2N·Fo.
The radar system has a transmitter for transmitting the signal of frequency 2N·Fo output from the frequency multiplier to a target as a transmitted signal; a receiver for receiving the signal of frequency 2N·Fo transmitted from the transmitter and reflected by the target; a mixer for mixing the signal received by the receiver with the signal of frequency Fo which is the signal distributed by the distributor and functions as a local oscillator signal; and a signal processor for obtaining a signal necessary for calculating the position and relative velocity of the target from the signal mixed by the mixer.
The foregoing common radar system includes the distributor and the frequency multiplier in addition to the oscillator to obtain the signal of frequency Fo and the signal of frequency 2N·Fo, thereby complicating the circuit configuration of the radar system. In contrast, using a push-push oscillator disclosed in the following Patent Document 1 as the oscillator, for example, makes it possible to output both the signal of frequency Fo and signal of frequency 2N·Fo from different terminals and hence can simplify the circuit configuration.
Here, the push-push oscillator has two oscillating sections which are identical and symmetrical and operate in opposite phases.
Patent Document 1: Japanese Patent Laid-Open No. 2000-223944 (Paragraph [0017] and FIG. 1).
With the foregoing configuration, the conventional oscillator can output both the signal of frequency Fo and the signal of frequency 2N·Fo if it has the two oscillating sections which are identical and symmetrical and operate in opposite phases. However, since it must have two oscillating sections consisting of active elements, the circuit configuration become comparatively large. In addition, unless it is designed considering variations in the performance between the two active elements, it has a problem of being unable to output the signals of desired frequencies.
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide an oscillator capable of outputting the signal of frequency Fo and the signal of frequency 2N·Fo without using the two active elements.
Another object of the present invention is to provide a transmitter-receiver and a frequency synthesizer including the oscillator.